1. Field of the Invention
The present invention relates to a novel rotational position sensor for detecting a rotational angle of a rotary shaft of, e.g., a throttle valve for an internal combustion engine, and also relates to an electronically controlled throttle device for an internal combustion engine, which employs the rotational position sensor.
2. Description of the Related Art
There are hitherto known rotational position sensors each having a characteristic that the amount of change in a signal output is proportional to the amount of change in a rotational angle, as disclosed in Patent References 1 to 3. Patent Reference 1 (Japanese Patent No. 2920179) discloses a magnetic position sensor comprising a rotor core having an annular magnet fixed on the inner peripheral side of an annular yoke, and two half disk-shaped stator cores arranged on the inner peripheral side of the annular magnet with a Hall device disposed between the two stator cores. Patent Reference 2 (JP-A-2000-28314) discloses a magnetic rotational position sensor comprising a rotor having an half disk-shaped magnet formed integrally with an inner periphery of a loop-like pole piece, and a magnetic flux sensor arranged on the inner peripheral side of the loop-like pole piece. Patent Reference 3 (JP-A-2002-206913) discloses a non-contact rotational position sensor comprising a rotor having an annular magnet, and a stator having two magnetic plates arranged above and below the rotor with a Hall device disposed between the two magnetic plates.